dotnet/wpf · error · ArgumentException

SR.InvalidStylusPointDescriptionSubset

Error message

SR.InvalidStylusPointDescriptionSubset

What it means

StylusPointCollection.Reformat(StylusPointDescription, GeneralTransform) throws ArgumentException when subsetToReformatTo is not a subset of the collection's current Description. Reformat can only drop or keep properties; it cannot invent packet properties the source points don't already carry.

Solutions

  1. Build the target description as a subset of spc.Description (e.g. via StylusPointDescription.GetCommonDescription)
  2. Check subsetToReformatTo.IsSubsetOf(spc.Description) before calling Reformat
  3. Re-capture stylus data with the needed packet properties instead of reformating existing points

Example fix

// before
var converted = spc.Reformat(richDescription, null);
// after
var common = StylusPointDescription.GetCommonDescription(richDescription, spc.Description);
var converted = spc.Reformat(common, null);
Defensive patterns

Strategy: validation

Validate before calling

if (!subsetToReformatTo.IsSubsetOf(spc.Description))
    subsetToReformatTo = StylusPointDescription.GetCommonDescription(subsetToReformatTo, spc.Description);

Type guard

bool CanReformat(StylusPointCollection spc, StylusPointDescription to) => to.IsSubsetOf(spc.Description);

Try / catch

try { var r = spc.Reformat(to, transform); } catch (ArgumentException ex) when (ex.ParamName == "subsetToReformatTo") { var r = spc.Reformat(StylusPointDescription.GetCommonDescription(to, spc.Description), transform); }

Prevention

When it happens

Trigger: Calling spc.Reformat(targetDescription, transform) where targetDescription contains StylusPointProperties absent from spc.Description — e.g. requesting pressure/button properties the device never captured.

Common situations: Converting strokes to a richer description expected by a downstream API; reformatting to a hardcoded description that doesn't match the actual tablet hardware's packet properties.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/1ebf310e358b4743. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Input/Stylus/Common/StylusPointCollection.cs:448

        }

        /// <summary>
        /// Reformat
        /// </summary>
        /// <param name="subsetToReformatTo">subsetToReformatTo</param>
        public StylusPointCollection Reformat(StylusPointDescription subsetToReformatTo)
        {
            return Reformat(subsetToReformatTo, System.Windows.Media.Transform.Identity);
        }

        /// <summary>
        /// Helper that transforms and scales in one go
        /// </summary>
        internal StylusPointCollection Reformat(StylusPointDescription subsetToReformatTo, GeneralTransform transform)
        {
            if (!subsetToReformatTo.IsSubsetOf(this.Description))
            {
                throw new ArgumentException(SR.InvalidStylusPointDescriptionSubset, nameof(subsetToReformatTo));
            }

            StylusPointDescription subsetToReformatToWithCurrentMetrics =
                StylusPointDescription.GetCommonDescription(subsetToReformatTo, 
                                                            this.Description); //preserve metrics from this spd

            if (StylusPointDescription.AreCompatible(this.Description, subsetToReformatToWithCurrentMetrics) && 
                (transform is Transform) && ((Transform)transform).IsIdentity)
            {
                //subsetToReformatTo might have different x, y, p metrics
                return this.Clone(transform, subsetToReformatToWithCurrentMetrics);
            }

            //
            // we really need to reformat this...
            //
            StylusPointCollection newCollection = new StylusPointCollection(subsetToReformatToWithCurrentMetrics, this.Count);
            int additionalDataCount = subsetToReformatToWithCurrentMetrics.GetExpectedAdditionalDataCount();

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